"Yes, those were horrible days for us, too, those days when Austria was attacked," Bartók responded from Budapest on April 13, 1938 to his loyal friend in Basle, Switzerland, Mrs. Oscar Müller-Widmann. "The most frightful thing for us at the moment is that we face the threat of seeing Hungary also given over to this regime of bandits and murderers. I cannot imagine how I could live in such a country.... Strictly speaking, it would be my duty to exile myself, if that is still possible. But even under the most favorable auspices, it would cause me an enormous amount of trouble and moral anguish to earn my daily bread in a foreign country.... All this adds up to the same old problem, whether to go or stay."

Given the unsettled and frightening political situation under which all eastern Europeans found themselves during the terrible days of 1938 and 1939, it is little wonder that Bartók's creativity was undermined. He managed to complete the Violin Concerto No. 2 in December 1938, but then became too preoccupied with the deteriorating life around him to undertake any further original work. Paul Sacher, the conductor of the Basle Chamber Orchestra and a close friend who had commissioned the Music for Strings, Percussion and Celesta two years before, recognized that Bartók needed to leave Budapest if his creativity was to be revived, so he invited the composer and his wife to spend the summer of 1939 at his chalet at Saanen in the massif of Gruyère in Switzerland and then asked him to write a new work for his orchestra. Bartók accepted both of the invitations and arrived at Saanen in July. Even in Switzerland, however, Bartók could not escape the ominous European political situation. "The poor, peaceful, honest Swiss are being compelled to burn with war-fever," he wrote to his son Béla in Hungary on August 18th.

Once installed at Saanen, however, Bartók retreated into a welcome isolation to undertake Sacher's commission. "Fortunately I can put this [war] worry out of my mind if I have to," he continued in his letter to Béla. "I have to work: a piece for Sacher himself (something for a string orchestra). Luckily the work went well, and I finished it in fifteen days. I just completed it yesterday." The work was the Divertimento for String Orchestra, one of Bartók's most immediately accessible compositions. The halcyon Swiss interlude during which he produced this piece was not to last, however. Almost as soon as he had begun the Sixth Quartet at Saanen, word came from Budapest of his beloved mother's death. He returned home, where he completed- though with considerable difficulty-the Quartet in November 1939. It was the last work that he wrote in Europe, and his last until the Concerto for Orchestra four years later. His situation in Budapest became untenable during the following months, and in April 1940, he sailed to America for a concert tour with the violinist Joseph Szigeti. After an arduous journey home that summer to settle his affairs and collect his wife, he went back to New York in October and never again saw Hungary. The Quartet was premiered in New York on January 20, 1941 by the Kolisch Quartet.

The noted French musicologist Harry Halbreich wrote that the Quartet No. 6 "appeals to us as an intensely moving human document with a foundation that is at least autobiographical, if not also that of ‘program music.' Bartók's iron grip, which formerly kept under control every outburst, however violent, of the composer's temperament, here gives way to a subjectivity and directness of expression that make this one of the most moving and easily appreciated of Bartók's works." The Quartet takes as its motto an arching, step-wise melody marked Mesto-"sad"- given at the beginning by the unaccompanied viola. This theme unifies the whole composition by reappearing in different settings at the beginnings of the second and third movements, and by serving as the principal subject of the finale. The first movement is a sonata form based on a flying main theme and a second theme grown from the vibrant rhythms and winding melodic leadings of Hungarian folksong. The dotted-rhythm Marcia, savagely ironic and unsettlingly diabolical, is strongly contrasted by the gapped-scale melody and rustling accompaniment of the central trio. The bitter, menacing humor of the Burletta ("Burlesque") is ameliorated, though not overcome, by the pastoral music of the movement's internal episodes. The finale unfolds dolefully from the Mesto theme, allowing ghostly reminiscences of the two themes from the first movement before giving one final loud wail and ebbing into silence. Each successive movement of the Sixth Quartet is more melancholy in mood and slower in tempo-Vivace, Marcia, Moderato, Mesto-so that the work ends with a feeling of bleak resignation, perhaps indicating the growing pessimism that overcame Bartók during the time of its creation. "Nowhere in all Bartók's music is there a movement so restrained and at the same time with such a powerful impact," wrote Halsey Stevens of the finale in his study of the composer.